3 tanks and 2 containers can hold 24.9 litres of water.
1 tank and 1 container can hold 8.7 litres of water.

1. How many litres of water can 1 tank hold?
2. How many litres of water can 1 container hold?
3. How many litres of water can 5 containers hold?
4. How many litres of water can 4 containers and 3 tanks?

(a)
3 tanks + 2 containers = 24.9 --- (1)
1 tank + 1 container = 8.7 --- (2)

(2) x 2
1 tank + 1 container = 8.7
2 tanks + 2 containers = 8.7 x 2
2 tanks + 2 containers = 17.4 --- (3)

(1) - (3)
(3 tanks + 2 containers) - (2 tanks + 2 containers) = 24.9 - 17.4
3 tanks + 2 containers - 2 tanks - 2 containers = 7.5
3 tanks - 2 tanks + 2 containers - 2 containers = 7.5

1 tank = 7.5

Volume of 1 tank = 7.5 ℓ

(b)
Substitute 1 tank = 7.5 into (2).
1 tank + 1 container = 8.7
7.5 + 1 container = 8.7

1 container = 8.7 - 7.5 = 1.2

Volume of 1 container = 1.2 ℓ

(c)
Volume of 5 containers
= 5 x 1.2
= 6 ℓ

(d)
Volume of 4 containers and 3 tanks
= 4 x 1.2 + 3 x 7.5
= 4.8 + 22.5
= 27.3 ℓ

Answer(s): (a) 7.5 ℓ; (b) 1.2 ℓ; (c) 6 ℓ; (d) 27.3 ℓ